//FIXME Not checked on threadsafety yet; after checking please remove this line
/* crypto/idea/i_skey.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The license and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution license
 * [including the GNU Public License.]
 */

#include "idea.h"
#include "idea_lcl.h"

static IDEA_INT inverse(unsigned int xin);
void idea_set_encrypt_key(const unsigned char *key, IDEA_KEY_SCHEDULE *ks)
{
	int i;
	register IDEA_INT *kt, *kf, r0, r1, r2;

	kt = &(ks->data[0][0]);
	n2s(key, kt[0]);
	n2s(key, kt[1]);
	n2s(key, kt[2]);
	n2s(key, kt[3]);
	n2s(key, kt[4]);
	n2s(key, kt[5]);
	n2s(key, kt[6]);
	n2s(key, kt[7]);

	kf = kt;
	kt += 8;
	for(i = 0; i < 6; i++)
	{
		r2 = kf[1];
		r1 = kf[2];
		*(kt++) = ((r2 << 9) | (r1 >> 7)) & 0xffff;
		r0 = kf[3];
		*(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
		r1 = kf[4];
		*(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
		r0 = kf[5];
		*(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
		r1 = kf[6];
		*(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
		r0 = kf[7];
		*(kt++) = ((r1 << 9) | (r0 >> 7)) & 0xffff;
		r1 = kf[0];
		if(i >= 5) { break; }
		*(kt++) = ((r0 << 9) | (r1 >> 7)) & 0xffff;
		*(kt++) = ((r1 << 9) | (r2 >> 7)) & 0xffff;
		kf += 8;
	}
}

void idea_set_decrypt_key(IDEA_KEY_SCHEDULE *ek, IDEA_KEY_SCHEDULE *dk)
{
	int r;
	register IDEA_INT *fp, *tp, t;

	tp = &(dk->data[0][0]);
	fp = &(ek->data[8][0]);
	for(r = 0; r < 9; r++)
	{
		*(tp++) = inverse(fp[0]);
		*(tp++) = ((int)(0x10000L - fp[2]) & 0xffff);
		*(tp++) = ((int)(0x10000L - fp[1]) & 0xffff);
		*(tp++) = inverse(fp[3]);
		if(r == 8) { break; }
		fp -= 6;
		*(tp++) = fp[4];
		*(tp++) = fp[5];
	}

	tp = &(dk->data[0][0]);
	t = tp[1];
	tp[1] = tp[2];
	tp[2] = t;

	t = tp[49];
	tp[49] = tp[50];
	tp[50] = t;
}

/* taken directly from the 'paper' I'll have a look at it later */
static IDEA_INT inverse(unsigned int xin)
{
	long n1, n2, q, r, b1, b2, t;

	if(xin == 0)
		{ b2 = 0; }
	else
	{
		n1 = 0x10001;
		n2 = xin;
		b2 = 1;
		b1 = 0;

		do
		{
			r = (n1 % n2);
			q = (n1 - r) / n2;
			if(r == 0)
			{
				if(b2 < 0) { b2 = 0x10001 + b2; }
			}
			else
			{
				n1 = n2;
				n2 = r;
				t = b2;
				b2 = b1 - q * b2;
				b1 = t;
			}
		}
		while(r != 0);
	}
	return ((IDEA_INT)b2);
}
